The invention relates to a process for improving the filling capacity of tobaccos by treating the tobacco with a gas under pressure and subsequent heating after pressure relief, in which the tobacco is treated with nitrogen and/or argon at working pressures up to 1000 bar and at an operating temperature in the range of 0.degree. to 50.degree. C. followed, after pressure relief, by brief thermal aftertreatment.
Such a process is known e.g. from DE-OS No. 29 03 300 and related Ziehn U.S. Pat. No. 4,289,148, in which the tobacco firstly undergoes high pressure gas treatment and then thermal aftertreatment. The high pressure gas treatment leads to the tobacco absorbing gas, the tobacco absorbing a sufficiently large quantity of gas as a result of the high final pressure, the short pressure reduction times and a possible moistening of the tobacco prior to treatment. During the subsequent thermal after-treatment, the occluded gas expands as a result of the external heat supply and produces an outwardly directed pressure and consequently a swelling of the tobacco structure. The entire disclosure of the Ziehn U.S. Pat. No. 4,289,148 is hereby incorporated by reference and relied upon.
The experts have hitherto been of the opinion that the improvement to the filling capacity increases with the proportion of gas absorbed and it was also assumed that the tobacco used should have some initial moisture content.
It has been considered a disadvantage of the known process that a tobacco being thus treated frequently formed cohesive intermingled strands of tobacco following high pressure gas treatment, resulting in possible difficulties during the thermal aftertreatment.
The problem of the present invention is to improve the process of DE-OS No. 29 03 300 and the Ziehn U.S. patent in such a way as to further increase the filling capacity of tobacco in a simpler and more energy-saving manner.